Electric wave signaling system



Dec. 1-1, 1928. 1,695,039

' L. M. CLEMENT I ELECTRIC WAVE smmmue SYSIBI Filed Sept. 1, 1925 1.1 /2 AMPLIFIER fig. 2.

by My.

Patented Dec. 11, 192s.

UNITED STATES PATENT oFFicE, A

LEWIS M. CLEMENT, OF MOUNTAI'N LAKES, NEW JERSEY, ASSIGNOR TO BELL TELE- PHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK. I Y

ELECTRIC WAVE SIGNALING SYSTE1VL Application filed September 1, 1925'. Serial 1T0. 53;784.

This invention relates to electrical ave A feature of the invention is a space dissignaling systems, and more particularly to charge oscillation generator adapted to-be improved means for controlling electric controlled by a telegraph key and havingf55 Waves for telegraph signaling. choke coils of suitable inductanceand suit- 5 In space discharge tube systems wherein ably arranged tocontrol the oscillationsso signaling is effected by successively starting asto eliminate certain side frequency comandstopping the oscillations in a space disponents produced When signaling, and a path charge tube, the envelope of the resultant in shunt to the inductance, including another Waves is ordinarily substantially rectangular inductance and a key.

1 in form. This wave form results because the The invention comprises a space discharge impedance of the path traversed by the osciloscillation generator including a. space dislations including the space path of the'tubeis charge tube and means for varying the tube" ordinarily non-reactive and is varied in an impedance, which means includes reactive abrupt manner between its normal value and elements designed to causethe amplitude of infinity. I the .WQLVGS' to increase and decrease at a rate The nature of a train of oscillations Which such thatthe number of side frequency comhavebeen 'brokenup into elements of recponents is reduced. U tangular envelope is Well known; An oscil- More specifically, theinvention mayin lation train of this character 1nay be conclude a space discharge tube oscillation gen- 20 sidered, in its effects, as comprising a normal erator adaptedto be controlled byja tele- Wave of the oscillator frequency anda Whole graph keyfor stopping and starting the 0s series of Waves of various frequencieseXtendcillations in accordance with signals. The" ing through the range at each side of'the'norkey is so arrangedthat When closed it short: malwave and being spaced therefrom at incircuits an impedance a POrtiOnbfrWliiCh is 25 tervals dependent upon the rate'and the dur'ainc-luded in'both the-input and outp'utcircuit's tion of. the interruptions. If'thecornersof of the space discharge tube,-thereby-reducing the rectangular envelopes of the train elethe negative potential on thegridofthetube ments are rounded off, many of the side freand causing oscillationsto be generated. The so quencies most remote from the -normal Wave impedance includes an inductancefelement' 0 disappear. As a result the effective vave for controlling the rateof decay ofthe osband utilized for signal transmission is' 11arcillations when the key is open. Another r w d; I inductance element is also included in series 7 It is an object of this invention to control With the key to reduce the rate of building up electric Waves in accordance with signals and of the oscillations When the key is closed. I

5 to cause the envelopeofthe controlled Waves Theoscillation generatormay form. apart to have a'forin such that certainundesired' of a radio 't-ransmitteror a Wire signaling side frequencies are eliminated Without subsystem. i I stantial distortion of the signals. The reduction in number of sidefrequency Another object is to interrupt electrical os- Waves'generated in theoscillator reduces the 40 cillations in accordance with signals and to WlClt-lYO-f the band of frequenciesoccupied by reduce the Width of the band of frequencies thesignals and hence reduces the likelihood necessary for the transmission of intelligible of interference With other signal channels or signals. A C systemsfoperating', on'diiferentwave lengths A furtherobject is to transmit signals or carrier ave frequencies. A Thefnumberof interrupting electrical oscillations in suchja' possible signal channels Withi'n'a given range manner thatithe resultant Wave envelope'has of frequencies is also increased. I

ingeneral a rectangular form with rounded In the drawings, Fig.1 represents a radio corners as illustrated.

v An additional object is to control electrical the invention. q

oscillations by variablyimpeding the 'osc-il- Fig. 2' represents approximately the form lations at a rate such that anumber of side of wavesproducedjby 'appli'cants invention;

frequency components are elimiI' a-ted. The following is a detailed description'of' telegraph transmitting system embodying the system illustrated in Fig. 1. The system includes an oscillation generator 10 adapted to be controlled by a telegraph key 11 to supply signal waves to an amplifier 20 connected to an antenna 25. a

The oscillation generator 10, which is of the general type disclosed in Patent 1,356,- 763, to R. V. L. Hartley, October 26, 1920, includes a s ace discharge tube 12 having an input circuit, including inductance 13 and resistance 14, connected between its control electrode and cathode. Tube 12 is also included in a space current circuit, comprising inductance 15, direct current generator 16, inductance 17 and resistance 14, connected between its anode and cathode.

The resistance 14 is included in both the input and the output circuits of tube 12. 'lhese circuits are coupled by an adjustable condenser 18 connected to terminals of coils l3 and 15, adjacent to the control. electrode and anode, respectively, of tube 12. The opposite terminals of inductances 13 and 15 are each connected to the cathode of tube 12 by condensers 19 and 21, respectively.

The circuit, formed by inductances 13 and 15 and condensers 18, 19 and 21 is tuned to the frequency at which Waves are to be generated in oscillator 10, the condensers 19 and 21 being preferably of such large capacity as to have negligible effect upon the tuning of the circuit.

The condenser 19 serves as a low impedance path for the oscillations in the input circuit of tube 12, in shunt to resistance 14, and condenser 21 provides a similar low impedance path for oscillations in the output circuit, in shunt to generator 16, inductance 17 and resistance 14.

A path,including telegraph key 11 and an inductance 22, is adapted to be closed in shunt to the resistance 14 and inductance 17 upon the closure of the key. The telegraph key is shunted by condenser 23 in series with resistance 24, for preventing sparking at the contacts.

The cathode and anode of tube 12 are also connected to the input terminals of amplifier 20, which may be of any well-known type such, for example, as a space discharge tube amplifier. The output terminals of the amplifier 20 are connected, respectively, to the antenna 25 and-to ground.

In the operation of the system, for the transmission of signals, the key 11, being suc- V cessively closed and opened, alternatelyconnects and disconnects the path, includinginductance 22, around the resistance 14 and inductance 17. c

When key 11 is closed, the negative potential upon the control electrode of tube 12 is reduced and when key 11 is opened the negative potential is increased to the extent of the drop in potential along resistance 14. The change of potential is affected by the inductance 17 in such manner as to tend to cause the envelope of the oscillations to have a form approximately like that illustrated in Fig. 2.

The inductance 22 affects the space current of tube 12 in such manner as to tend to assist the coil 17 in producing the form of en velope illustrated in Fig. 2. WVithout the coil 22 the space current might surge in the following path: anode of tube 12, inductance 15, generator 16, key 11 or resistance 24 and condenser 23 to the cathode of tube 12. Inductance 15, being merely a radio frequency choke coil, has negligible effect upon low frequency surges in the space current. Theinductance 22 is provided. for preventing an abrupt change of space current when the space path impedance is varied by key 11. When the negative potential on the grid is reduced, the oscillations in the system build up gradually from small amplitude to large amplitude and when the negative potential.

on the control electrode is increasedthe oscillations die out gradually.

Resistance 14 preferably is of such value as to supply suflicient negative potential to the control electrode to increase the impedance of the space path of tube 12 sufi'iciently to stop the oscillations. It may, however, be of such value as to merely reduce the oscillations to very small amplitude or to complete ly block the space current in the tube.

The effect or inductances 17 and 22 upon the envelope of the oscillations, that is, upon the shape of the curve representing change in amplitude ofthe oscillation isillustrated in Fig. 2. I i

The waves illustrated are, in general, of rectangular form, but have the corners rounded off. The rounding oil is produced by the action of inductances 17 and 22 in changing the rate of increase and decrease of the amplitude of the oscillations as already expained. l

The amplitude of the oscillations is not affected directly by inductances 14 and 22, because the oscillations are prevented from traversing these inductances by condenser. 21, but the amplitude is affected indirectly through the effect of the inductancesupon the impedance of the space current circuit oi. the tube 12 in the manner set forth. f

Although this invention has been. illustrated and described as embodied in a specific circuit, it is capable of more general application and it is intended that it should be limited only by the appended claims.

What is claimed is:

1. In combination, a space discharge tube, input and output circuits forsaid tube, an impedance included in both] said circuits, an inductance in series with saidimpedance' in one of said circuits, and a path adapted to be 4. In a telegraph transmitting system, a space dlscharge repeater having an output circuit, a resistance and an inductance included in series 111 sald output circuit, and a path includ ng a second inductance, andra telegraph key adapted to connect said second.

inductance in shunt to said resistance and said first named lnductance.

5. In an oscillation generator, a space discharge tube, input and output circuits for said tube, a resistance includedm both said circuits, an inductance included in said output circuit, and means for short-circuiting said resistance.

6. In an oscillation. generator, a space discharge tube, input and output circuits for said tube, an impedance included in both said circuits, and a path including a choke coil adapted tobe connected in shunt to said impedance.

7. In an oscillation generator, a space discharge tube, input and output circuits for said tube, a resistance included in both said circuits, and means for short-circuiting said reslsta-nce, sald' means includlng tWO 1n- I ductances, one of said inductances being included in said output circuit.

8. In an oscillation generator, a space discharge tube, input and output circuits for said tube, said output circuit including a path comprising an inductance and a resistance,

and a path, including a condenser, in parallel with said first path, said condenser having low impedance for oscillations, and means for connecting a third pathincluding an inductance in parallel with said first two paths for producing signals.

In Witness whereof, I hereunto subscribe my name this 28th day of August A. D., 1925.

LEWIS M. CLEMENT. 

